1. Field of the Invention
The present invention relates to improvements in structure of a solid electrolytic capacitor.
2. Description of the Background Art
Referring to FIGS. 7 to 9, an example of the structure of a solid electrolytic capacitor will be described.
This solid electrolytic capacitor includes therein a cube-shaped Ta sintered body 1, as well as a dielectric oxide film 2, a polymer layer 3, a carbon layer 4, and a silver paste layer 5 that surround Ta sintered body 1. Ta sintered body 1 is provided with a cylindrical tantalum wire 1a protruding outside via dielectric oxide film 2.
In the solid electrolytic capacitor, tantalum wire 1a forms an anode portion while silver paste layer 5 forms a cathode portion. Here, in the following description, the tantalum wire is referred to as anode portion 1a and the silver paste layer is referred to as cathode portion 5. Further, Ta sintered body 1, dielectric oxide film 2, polymer layer 3, carbon layer 4, and silver paste layer 5 are collectively referred to as a capacitor element 10.
To anode portion 1a, a plate-shaped anode terminal 20 is electrically joined by resistance welding. To cathode portion 5, a plate-shaped cathode terminal 30 is electrically joined using an electrically conductive adhesive 40 such as silver adhesive. Cathode terminal 30 includes as shown in FIGS. 7 and 9 a flat portion 30a connected to cathode portion 5 and a lead portion 30b extended to the outside. A solid electrolytic capacitor having such a structure as described above is disclosed in Patent Document 1 (Japanese Patent Laying-Open No. 08-022932).
Here, flat portion 30a of cathode terminal 30 is connected to cathode portion 5 using electrically conductive adhesive 40. In a process of manufacturing the solid electrolytic capacitor, if an external force is applied to cathode terminal 30, cathode terminal 30 could be peeled off from cathode portion 5. After completion of the solid electrolytic capacitor, heat could cause cathode terminal 30 to be peeled off from cathode portion 5.
In the case where cathode terminal 30 is peeled off from cathode portion 5 due to any of the above-described factors, the equivalent series resistance (ESR) could increase and/or a failure such as open circuit could occur, possibly resulting in deterioration in reliability of the solid electrolytic capacitor.